JP5602139B2 - Products used for magnetic heat exchange, intermediate products, and manufacturing methods for products used for magnetic heat exchange - Google Patents

Description

  The present invention relates to a product used for magnetic heat exchange and a method for manufacturing a product used for magnetic heat exchange.

  The magnetocaloric effect refers to adiabatic conversion of a magnetically induced entropy change to heat generation or absorption. Thus, applying a magnetic field to a magnetocaloric product can induce entropy changes that result in the generation or absorption of heat. This effect is used to provide cooling and / or heating.

  Magnetic heat exchange devices such as those disclosed in US Pat. No. 6,676,772 typically exhibit a pump recirculation system, a heat exchange medium such as a liquid coolant, and a magnetocaloric effect. A chamber filled with particles of magnetically cooled working product and means for applying a magnetic field to the chamber.

  A magnetic heat exchange device is in principle more energy efficient than a gas compression / expansion cycle system. Also, the magnetic heat exchange device is considered environmentally friendly because it does not use chemical products such as chlorofluorocarbons (CFCs) that are believed to contribute to a decrease in ozone concentration.

_{Recently, La (Fe l-a Si} a) l3, Gd 5 (Si, Ge) 4, Mn (As, Sb), and MnFe (P, As) products having a Curie temperature _{T c} is close to room temperature or the like Has been developed. The Curie temperature is the operating temperature of the product of the magnetic heat exchange system. Therefore, these products are suitable for use in applications such as building temperature control, household and industrial refrigerators and freezers, and automobile temperature control.

  As a result, magnetic heat exchange systems will indeed evolve to understand the benefits provided by new magnetic materials. However, it is desirable to be able to apply the magnetic heat exchange technology to a wider range for further improvement.

US Pat. No. 6,676,772

  It is an object of the present invention to provide a product comprising at least one magnetocalorically active phase and a method for producing the same that is used in a magnetic heat exchange device that can be produced cost-effectively.

By the method for producing a product impurities is not more than 5% by volume comprising at least one magnetocalorically active phase, at least one _{(La 1-a M a)} (Fe 1-b-c T b Y c) 13-d Xe A product provided by an intermediate comprising the phases of Here, 0 ≦ a ≦ 0.9, 0 ≦ b ≦ 0.2, 0.05 ≦ c ≦ 0.2, −1 ≦ d + 1, 0 ≦ e ≦ 3, and M is Ce, Pr or Nd. 1 or more. T is one or more of Co, Ni, Mn and Cr. Y is one or more of Si, Al, As, Ga, Ge, Sn, and Sb. X corresponds to one or more of H, B, C, N, Li, and Be. The intermediate includes at least one permanent magnetic phase, and the intermediate is processed to remove at least one intermediate portion. Thereafter, the intermediate is heat treated to produce a final product comprising at least one _{(La 1-a M a)} (Fe 1-b-c T b Y c) of _13-d Xe phase.

  A permanent magnet is defined as a product containing a strong coercive force of 10 Oe or more.

  A method for producing a product containing at least one magnetocalorically active phase should provide a range that is expected in a method that can form a large block and / or unify two or more small products and / or cost-effectively produce them. Enable.

  In particular, when processing a product including a magnetocalorically active phase having a large area, for example, a block having an area of at least 5 mm or several tens of mm, the present inventor has a product having an expected area manufactured from a large product. It was observed that inadequate cracks formed in the product during processing with a limited number of.

The present inventors have further pyrolytic observed that can be avoided primarily to form an intermediate having at least one permanent magnetic phase by heat treating the product. The intermediate includes a coercive force of 10 Oe or more necessary to be defined here as a permanent magnet.

  Processing can proceed without producing improper cracks so that products manufactured from large products can increase loss reduction. The intermediate is further heat treated to form a magnetocalorically active phase and to provide a product suitable for use as a moving component of a magnetic heat exchange device.

  The method for producing the intermediate comprising at least one magnetocalorically active phase was chosen as optimal. The powder metallurgy method has an advantage that a block having a large area can be manufactured cost-effectively. Milling of a powder comprising a product comprising at least one magnetocalorically active phase, followed by a sintering reaction, milling of the precursor to be formed by compression or sintering to form a sintered product, compression Powder metallurgy methods such as sintering can be used. The intermediate can be produced by other methods such as casting, melt-solid spinning, or the method described in the present invention and then processed by the method of the present invention.

  A magnetocalorically active material is defined as a material whose entropy changes when placed in a magnetic field. For example, it may be the result of a change from ferromagnetism to paramagnetic behavior. The magnetocalorically active material can exhibit an inflection point where the sign of the second derivative of magnetization with respect to the applied magnetic field changes from positive to negative only in some temperature ranges.

  A magnetocalorically inactive material is defined as a material that does not exhibit a significant entropy change when placed in a magnetic field.

  The magnetic phase transition temperature is defined herein as a change from one magnetic state to another. The magnetocalorically active phase shows a change from antiferromagnetism to ferromagnetism associated with a change in entropy. The magnetocalorically active phase shows a change from antiferromagnetism to paramagnetism associated with a change in entropy. For these materials, the magnetic transition temperature is also called the Curie temperature.

  Without being bound by theory, the fact that the thermal decomposition of the product containing the magnetocalorically active phase was observed during processing is considered to be caused by a change in the temperature-dependent phase in the magnetocalorically active phase. . The phase change includes entropy change, change from ferromagnetic material to paramagnetic material, volume change, and linear thermal expansion change.

  In processing situations where the product is non-magnetocalorically active, there is no phase change that occurs during processing, and expansion associated with phase change can be avoided. Therefore, the product can be reliably processed to increase production and reduce losses.

  As an example, the intermediate has an alpha-Fe content of 50% by volume or more. The intermediate is expected to gradually decrease the proportion of the magnetocalorically active phase by gradually increasing the content of alpha-Fe.

  Further by way of example, the intermediate is heat-treated to produce a final product having an alpha-Fe content of 5% by volume or more.

The intermediate may be manufactured by heat treatment of a precursor having at least one phase having a NaZn ₁₃ type crystal structure.

The intermediate heat-treated precursor having at least one phase having a crystal structure of NaZn ₁₃ type, and degrading crystalline forms of NaZn ₁₃ type can be prepared by forming a permanent magnetic by stepwise heat treatment .

  In an embodiment, the precursor is heat treated at conditions selected to produce at least one alpha-Fe type phase.

  The precursor may be heat treated at conditions selected to produce a non-magnetic matrix containing at least one alpha-Fe type phase.

  The precursor may be heat treated to produce a product that includes at least one 60 vol% or more alpha-Fe type phase.

The precursor was stirred powder selected to provide at least one _{(La 1-a M a)} (Fe 1-b-c T b Y c) of _13-d Xe phase, at least one In order to produce a phase of NaZn ₁₃ type crystal structure, it can be produced by sintering at a temperature T1.

  After heat treatment at temperature T1, the precursor can be heat treated at temperature T2 to form an intermediate having at least one permanent magnetic phase. T2 <T1. The heat treatment at the temperature T1 and the temperature T2 is performed without cooling the product below the temperature T2. However, the heat treatment may be performed by cooling the precursor to room temperature after the heat treatment at the temperature T1.

The alpha-Fe type phase is formed at a temperature lower than the temperature necessary for forming the phase or the phase of the NaZn ₁₃ type crystal structure.

If the precursor has at least one NaZn ₁₃ type crystal structure phase, the temperature of T2 can be selected to decompose the NaZn ₁₃ type crystal structure phase. The alpha-Fe type phase can be formed after decomposing a phase having a NaZn ₁₃ type crystal structure.

As a further embodiment, the intermediate is magnetocalorically active phase _{(La 1-a M a)} (Fe 1-b-c T b Y c) temperature to produce the final product having a _13-d Xe Heat treated at T3. T3> T2. In the embodiment, T3 <T1.

In a further embodiment, the precursor composition is selected to cause a phase reversible reaction having a NaZn ₁₃ type crystal structure at temperature T2. After the decomposition of the phase having the NaZn ₁₃ type crystal structure at T2, the phase having the NaZn ₁₃ type crystal structure is re-formed at the temperature T3. T3 is a temperature significantly higher than T2.

  A portion of the intermediate can be removed by any method. For example, a part of the intermediate can be removed by machining or / and mechanical grinding or polishing, chemical mechanical polishing or / and discharge cutting, linear erosion cutting, laser cutting, drilling, water beam cutting, or the like.

  A combination of these methods can be used for each intermediate. For example, an intermediate can be singulated from two or more components by removing a portion of the intermediate by further removing by mechanical cutting to provide electrical discharge cutting or the final expected surface. . Finally, the through hole can be drilled with a laser drill to provide a passage for the heat transfer fluid.

  A portion of the intermediate can be removed to form a channel on the surface of the intermediate. For example, a channel that directs the flow of a heat exchange medium to produce a final product in a heat exchanger apparatus. A portion of the intermediate can be removed to provide a through hole. The through holes have the advantage of inducing the flow of the heat exchange medium and increasing the surface area of the final product, which can further improve the heat exchange efficiency between the product and the heat exchange medium.

An intermediate for producing a product having at least one magnetocalorically active phase is provided in the following configuration. At least one _{(La 1-a M a)} (Fe 1-b-c T b Y c) the phase of the _13-d Xe 5% by volume or less of impurities, 0 ≦ a ≦ 0.9,0 ≦ b ≦ 0.2, 0.05 ≦ c ≦ 0.2, −1 ≦ d + 1, 0 ≦ e ≦ 3, and M corresponds to one or more of Ce, Pr, and Nd. T is one or more of Co, Ni, Mn and Cr. Y is one or more of Si, Al, As, Ga, Ge, Sn, and Sb. X corresponds to one or more of H, B, C, N, Li, and Be. The intermediate includes a permanent magnet.

  The intermediate can be easily processed by, for example, machining, polishing, or linear erosion cutting. Large blocks can therefore be manufactured in a cost-effective manner as powder metallurgy technology. Manufactured to provide products with the expected area for special applications. Said processing can be performed separately.

  For example, a consumer can purchase to process an intermediate. These can then be heat treated to form a magnetocalorically active phase.

  Alternatively, the production of the intermediate and the heat treatment of the workpiece can be performed in an apparatus with appropriate equipment. The above processing can be carried out by different apparatuses having equipment suitable for processing, not equipment suitable for heat treatment.

  A product comprising at least one magnetocalorically active phase used in a magnetic heat exchange device can be produced cost-effectively by applying the intermediate in a wide range.

In embodiments, configuration of at least one of _{(La 1-a M a)} (Fe 1-b-c T b Y c) of _13-d Xe phases were selected to show the reversible phase decomposition reaction. This is completed by disassembling to provide an intermediate product as a first step and then subjecting it to a heat treatment.

At least one _{(La 1-a M a)} (Fe 1-b-c T b Y c) of the _13-d Xe phase configuration, at least one alpha -Fe based phase and La- rich and Si- rich It can be selected to show a reversible phase decomposition reaction into phases.

As a further embodiment, at least one _{(La 1-a M a)} (Fe 1-b-c T b Y c) of the _13-d Xe phase structure at least one _{(La 1-a M a)} (Fe phase _{1-b-c T b Y} c) 13-d Xe is selected to be formed by sintering in the liquid phase. This makes it possible to manufacture high-density products and high-density products in an acceptable time.

  As an embodiment, the intermediate body has the following configuration as a whole. a = 0, T is Co, Y is Si, and e = 0. Further, a = 0, T is Co, Y is Si, and when e = 0, 0 <b ≦ 0.075 and 0.05 <c ≦ 0.1.

  The intermediate may include at least one alpha-Fe type phase. In a further embodiment, the intermediate comprises more than 60% by volume of alpha-Fe type phase. The alpha-Fe type phase contains Co and Si.

  As an embodiment, the intermediate further includes a La-rich or Si-rich phase.

In further embodiments, the intermediate includes the following magnetic properties: B _r > 0.35T, H _cj > 80 / B _s > 1.0T.

  The intermediate may include a composite structure of a nonmagnetic matrix and a plurality of inclusions of alpha-Fe distributed in the nonmagnetic matrix. Among these, non-magnetism is related to the state of the matrix at room temperature, and includes paramagnetic and diamagnetic materials similar to ferromagnetic materials in a very small saturation polarization.

  The intermediate has a coercive force of 10 Oe to 600 Oe. Such coercive products are referred to as half hard magnets.

  The permanent magnet includes an alpha-Fe type phase.

In further embodiments, the intermediate exhibits a temperature dependent transition of length and volume at the reaction temperature. Here, (L _10% −L _90% ) × 100 / L <0.1. L is the length of the product, L _10% is _10% of the maximum length change, and L _90% is _90% of the maximum length change. The reaction temperature is room temperature. The intermediate contains a temperature dependent transition of length and volume at the reaction temperature due to thermal decomposition due to pressure by avoiding length and volume changes.

A product is provided comprising at least one magnetocalorically active LaFe ₁₃ base phase having a magnetic phase transition Tc and no more than 5% impurities. A configuration comprising at least one magnetocalorically active TLaFe ₁₃ base phase is selected to exhibit a reversible phase decomposition reaction.

The configuration of at least one LaFe ₁₃ base phase includes Si and is selected to exhibit a reversible phase decomposition reaction into at least one alpha-Fe base phase, La-rich or Si-rich phase.

Furthermore, as an embodiment, the content of Si is selected so that at least one LaFe ₁₃ base phase exhibits a reversible phase decomposition reaction into an alpha-Fe base phase, La-rich or Si-rich phase.

As a further embodiment, the configuration of at least one LaFe ₁₃ base phase is selected such that a LaFe ₁₃ -base phase is formed by liquid phase sintering.

Further, as an embodiment, the LaFe ₁₃ base phase has (La _1-a M _a ) (Fe _1-bc T _b Y _c ) _13-d Xe as follows. 0 ≦ a ≦ 0.9, 0 ≦ b ≦ 0.2, 0.05 ≦ c ≦ 0.2, −1 ≦ d + 1, 0 ≦ e ≦ 3, M is Ce, Pr, Nd, T is Co, Ni, Mn, and Cr, Y is Si, Al, As, Ga, Ge, Sn, Sb, and X are H, B, C, N, Li, and Be.

  Further, as an embodiment, a = 0, T is Co, Y is Si, e = 0/0 <b ≦ 0.075, and 0.05 <c ≦ 0.1.

  In further embodiments, the product includes a magnetocalorically active phase that exhibits a temperature-dependent transition in length or volume. The transition can occur in a temperature range above the temperature at which a measurable entropy change occurs.

The transition is manifested by (L _10% -L _90% ) × 100 / L> 0.2. Here, L is the length of the product, L _10% is _10% of the maximum value of the change in length, and L _90% is _90% of the maximum value of the change in length. This boundary is characterized by a sudden change in length per temperature T.

As an embodiment, the magnetocalorically active phase exhibits negative linear thermal expansion with increasing temperature. This behavior is illustrated by nafe ₁₃ type phase and _{(La 1-a M a)} (Fe 1-b-c T b Y c) magnetocalorically active phase comprising _13-d Xe type phase.

As a further embodiment, the magnetocalorically active phase product consisting particularly _{(La 1-a M a)} (Fe 1-b-c T b Y c) 13-d X based phase.

Further, as an embodiment, the product includes two or more magnetocalorically active phases having different transition temperatures _Tc .

  Two or more magnetocalorically active phases are randomly distributed in the product. On the other hand, the product includes a layer structure in which each layer is composed of a magnetocalorically active phase having a magnetic phase transition temperature different from that of other phases.

  In particular, the product may have a layer structure composed of a plurality of magnetocalorically active phases having a magnetic phase transition temperature that increases with the direction of the product and decreases in the opposite direction. Such an arrangement allows an increase in the operating temperature of the magnetic heat exchange device.

  A product comprising at least one magnetocalorically active phase having a magnetic phase transition temperature Tc is produced by manufacturing by the experimental method shown above. This product can be used for magnetic heat exchange as a component of a magnetic heat exchange device, for example.

  Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the alpha-Fe content of the precursor produced when sintered at 1100 ° C. FIG. 2 shows the alpha-Fe content of the precursor produced when sintered at 1080 ° C. FIG. 3 shows the alpha-Fe content of the precursor produced when sintered at 1060 ° C. FIG. 4 is a comparison with the results of FIG. FIG. 5 shows the alpha-Fe content of the precursor produced when sintered at 1080 ° C. FIG. 6 shows the alpha-Fe content of precursors produced with different contents in Table 3. FIG. 7A shows the precursor observed with a scanning electron microscope. FIG. 7B is an observation of the precursor of FIG. 7A, which has been heat-treated to synthesize an intermediate under effective conditions, with a scanning electron microscope. FIG. 8 shows a hysteresis curve of an intermediate having a structure of La (Fe, Si, Co) ₁₃ . FIG. 9 shows the temperature-dependent changes observed for the intermediate and product containing the magnetocalorically active phase. FIG. 10 describes the method of carrying out the intermediate as the first embodiment. FIG. 11 describes a method for carrying out an intermediate as the next embodiment. FIG. 12 illustrates a theoretical phase diagram that can occur in the La (Fe, Si, Co) ₁₃ phase due to the change in the Si content.

  The product including the magnetocalorically active phase can be manufactured by manufacturing an intermediate including the magnetocalorically active phase and heat-treating the precursor to form an intermediate having properties as a permanent magnet. The intermediate is processed to remove a portion and heat treated to form a magnetocalorically active phase.

  Formation of products that can function as intermediates

The phase of La (Fe, Si, Co) ₁₃ can be seen by the presence or absence of a magnetocalorically active phase, and therefore the workable state of the product can be inferred by measuring the alpha-Fe content. . The processable state of the intermediate is characterized by a high alpha-Fe content.

La (Fe, Si, Co) ₁₃ indicates a case where the total amount of Fe, Si, and Co is 13 when La is 1. The content of Fe, Si, and Co may vary, but the sum of the three components remains the same.

As a first embodiment, a heat treatment condition for inducing formation of a high alpha-Fe content in a sample composed of a magnetocalorically active La (Fe, Si, Co) ₁₃ phase was investigated.

  The alpha-Fe content was measured by a thermomagnetic method in which the magnetic polarization of the sample heated to the Curie temperature was measured as a function of the temperature of the sample in an external magnetic field. The Curie temperature of a mixture of several ferromagnetic phases can be measured, and the Aipha-Fe ratio can be measured using Curie-Weiss law.

  In particular, about 20 g of a thermally isolated sample can be heated to about 400 ° C. and produces permanent magnetism when placed in a Helm-holz-coil in an external magnetic field of about 5.2 kOe. . The magnetic flux is measured as a function of temperature as the sample is cooled.

A mixture of powders containing 18.85 wt% La, 3.6 wt% Si, 4.62 wt% Co is stirred and pulverized under protective gas conditions so that the average particle size becomes 3.5 μm. It was. The powder mixture was pressed at a pressure of 4 t / cm ² to form a block and sintered at 1080 ° C. for 8 hours. The sintered block has a density of 7.24 g / cm ³ . The block is heated at 1100 ° C. for 4 hours to provide a precursor, then heated at 1050 ° C. for 4 hours and rapidly cooled at 50 K / min. The precursor contains 4.7% alpha-Fe phase.

  Since the precursor had a dwell time of 4 hours at each temperature in order to synthesize a magnetic material having permanent magnetic properties, it was heated from 650 ° C. to 1000 ° C. in steps of 50 ° C. for a total of 32 hours. After heat treatment, the block contained 67.2% alpha-Fe phase.

The magnetic properties of the block were measured. The block had a coercive force _HcJ of 81 Oe, a remanence of 0.39 T, and a saturation magnetization of 1.2 T.

  A mixture of powders containing 18.39 wt% La, 3.42 wt% Si, 7.65 wt% Co was stirred, ground under protective gas conditions, pressed to form a block, Sintered at 1080 ° C. for 4 hours for synthesis.

  The precursor was heated at 750 ° C. for 16 hours to have permanent magnetism. After heating, the precursor was observed to contain over 70% alpha-Fe phase.

  The precursor was then heated at 650 ° C. Those having a dwell time of 80 hours at 650 ° C. contained more than 70% of the alpha-Fe phase.

  A mixture of powders containing 18.29 wt% La, 3.29 wt% Si, 9.68 wt% Co is stirred, ground under protective gas conditions, pressed to form a block, Sintered at 1080 ° C. for 4 hours for synthesis.

  The precursor was heated at 750 ° C. When the dwell time was 80 hours, a material containing 70% or more of an alpha-Fe phase was obtained.

  Comparing Examples 2 and 3, it was observed that the temperature and dwell time for synthesizing a magnetic material containing 70% or more of the alpha-Fe phase depends on the composition of the precursor.

  The magnetic material is expected to have improved mechanical properties as the content of the alpha-Fe phase increases.

  Effect of heat treatment temperature on alpha-Fe content

  The effect of temperature on the alpha-Fe content was investigated with the precursors produced by the powder mixtures of Examples 2 and 3. The results are summarized in FIGS.

  The powder mixtures of Examples 2 and 3 were pressed to block and sintered at 3 different temperatures of 1100 ° C, 1080 ° C and 1060 ° C for 4 hours. To synthesize the precursor, a vacuum was applied for the first 3 hours, and argon was injected for the last 1 hour.

  The precursor, a composite that was sintered in three different types, was injected with argon for 6 hours and heated at 1000 ° C., 900 ° C., and 800 ° C. for 6 hours. The content of alpha-Fe was measured. The results are summarized in FIGS.

  More alpha-Fe content was observed in samples heat treated at 800 ° C. than samples heat treated at 900 ° C. or 1000 ° C.

  FIG. 4 shows a comparison of the two types of samples in FIG. Further, it is shown that the inclusion of alpha-Fe at each temperature depends at least on the composition of the sample.

  FIG. 5 shows the alpha measured for a pre-sintered precursor that had been heat treated from 650 ° C. to 1080 ° C. to produce an intermediate having the characteristics of a permanent magnetic material and had a configuration consistent with Samples 2 and 3. The content of Fe is shown in the graph.

  These experimental results show that, in particular, the dwell time is 4 hours in this experiment, which is the optimal temperature for synthesizing high alpha-Fe content.

  When the heat treatment time was 4 hours, the maximum content of alpha-Fe in Sample 2 was observed at 750 ° C. The temperature of Sample 2 was 800 ° C. These results also show that the optimal heat treatment conditions for high alpha-Fe content depend on the precursor composition.

  Effect of heat treatment time on alpha-Fe content

  In additional experiments, the effect of heat treatment time on alpha-Fe content was investigated.

  When Examples 2 and 3 were compared, heat treatment was performed at 650 ° C., 700 ° C., 750 ° C., and 850 ° C. for different times, and the content of alpha-Fe was measured. The results are summarized in Tables 1 and 2.

  These results show that the content of alpha-Fe increases as the heat treatment time is increased at each temperature as a whole.

  Effect of cooling rate on alpha-Fe content

  In the case of a slow cooling rate, the precursor was sintered to produce a magnetocalorically active phase having a Curie temperature and having the configuration shown in Table 3.

  The configuration shown in Table 3 is referred to as the metal content of the precursor and is indicated by the subscript m. The metal content of the component is different from the content of the entire component. Ultimately, the modified content is related to the total metal content to give the metal content.

  A very slow cooling rate was assumed by heating at 1100 ° C. for 4 hours and rapidly cooling to determine the alpha-Fe content. Later, the temperature was reduced at 50 ° C. intervals and heated at each temperature for 4 hours before rapid cooling. The alpha-Fe content was measured after heat treatment at each temperature. The results are shown in FIG. 6 and summarized in Table 4.

  It was observed that the alpha-Fe content increased with decreasing temperature in all samples. In contrast to the example shown in FIG. 5, the sample with a high Co content has a higher content of alpha-Fe than the sample with a low Co content.

  Microstructures and phases distributed in precursors and intermediates

FIG. 7a shows a scanning electron micrograph of a precursor having a composition of 3.5 wt% Si, 8 wt% Co sintered at 1080 ° C. for 4 hours. This precursor contains a base phase of La (FeSiCo) ₁₃ which is a magnetocalorically active phase.

  FIG. 7b shows the scanning electron micrograph of FIG. 7a after heat treatment at 850 ° C. for 66 hours. The block contains phases characterized by having different contrast areas in the micrograph. Bright areas are measured by EDX analysis.

  Magnetic properties of intermediates

FIG. 8 shows the hysteresis curve of an intermediate composed of La (Fe, Si, Co) ₁₃ with 4.4% Co slowly cooled from 1100 ° C. to 650 ° C. over 40 hours, 67% The alpha-Fe content was measured. The measurement results of the magnetic properties are summarized in Table 5. The samples, _{B r} is _0.394T, is _{H cB 0.08kOe, H cJ} is 0.08kOe, _{(BH) max} was 1 kJ / ^{m 3.}

  Thermal expansion of intermediate and final products

FIG. 9 shows the thermal expansion at temperatures from 50 ° C. to + 150 ° C. for a product of La (Fe, Si, Co) ₁₃ composition with heat treatment in a workable state and magnetocalorically active state and 4.4% Co. Show.

  The first 3 hours in vacuum and the remaining 1 hour in argon atmosphere for a total of 4 hours at 1100 ° C. The product sintered at 1100 ° C. for 4 hours in argon atmosphere to provide an intermediate in the workable state at 800 ° C. The heat-treated intermediate has a content of 71% alpha-Fe and is shown to be positive in length with increasing temperature near 0 ° C. and mostly linearly changes.

The intermediate is further heat treated at a high temperature of 1050 ° C. for 6 hours to provide a final product containing a magnetocalorically active La (Fe, Si, Co) ₁₃ base phase with an alpha-Fe content of 2% or less. The final product shows a negative change of -0.44% in length with increasing temperature in the range of -50 ° C to + 40 ° C.

  When ready for processing, the product does not show a significant change in length. In particular, there is no significant negative change at temperatures near the Curie temperature.

  Without being bound by theory, large changes in the temperature range were observed in the heated product due to the heat generated during the processing of the final product. This change in product length is believed to be due to cracks observed in the processing of products containing magnetocalorically active phases. The decomposition of the magnetocalorically active phase results in the product exhibiting a slight positive increase in length, different thermal expansion behavior in the examples.

  Intermediate and final product mechanical properties

  The compressive strength of the intermediate and final product in the workable state was measured.

The product containing 4.4 wt% Co had a compressive strength of 1176.2 n / mm ² and a modulus of elasticity of 168 kN / mm ² in a processable state. The final organism had a compressive strength of 657.6 n / mm ² and an elastic modulus of 155 kN / mm ² .

The product containing 9.6 wt% Co had a compressive strength of 1123.9 n / mm ² and a modulus of elasticity of 163 kN / mm ² in a processable state. The final organism had a compressive strength of 802.7 n / mm ² and an elastic modulus of 166 kN / mm ² .

  The intermediate can be processed by milling or wire erosion cutting to provide two or more small intermediates from a large intermediate.

  Intermediate processing

  In an example, an intermediate of 23 mm × 19 mm × 6, 5 × mm having a configuration of La 18.55 wt%, Co 4.64%, Si 3.60% is simply formed by linear erosion cutting into a plurality of products having an area of 11.5 mm × 5.8 mm × 0.6 mm. It was unified.

  In an example, an intermediate of 23 mm × 19 mm × 6, 5 × mm having a configuration of La 18.72 wt%, Co 9.62%, Si 3.27% is simply formed by linear erosion cutting into a plurality of products having an area of 11.5 mm × 5.8 mm × 0.6 mm. It was unified.

FIG. 10 describes the experimental method of the intermediate 1 containing the magnetocalorically active phase 2. The magnetocalorically active phase 2 is a La (Fe _1-ab Co _a Si _b ) ₁₃ base phase, and the magnetic phase transition temperature T _c is 44 ° C. In this phase, the magnetic phase transition temperature is expressed as the Curie temperature at which the phase transitions from a ferromagnetic material to a paramagnetic material.

  In an embodiment, the intermediate 1 is formed by a powder metallurgy technique. In particular, a suitably blended powder mixture is compressed and sintered to form the intermediate. However, the processing method applied is essentially for products containing one or more magnetocalorically active phases that are produced by other methods such as casting or sintering a precursor having a magnetocalorically active phase. Can be used.

The precursor was heat treated at a temperature T1 selected to cause liquid phase sintering of the La (Fe _1-ab Co _a Si _b ) ₁₃ base phase. The precursor was further heat treated at a temperature T2. T2 <T1 to provide an intermediate that contains no more than 5% of a magnetocalorically active material that is reliably processed by a machining method such as linear erosion cutting to remove a portion of the intermediate. ,

  In the first embodiment, the intermediate body 1 is processed by mechanical milling and is shown diagrammatically in FIG. In particular, FIG. 1 shows mechanical milling of the outer surface 4 of the product. The position of the outer surface 4 of the product in the manufactured state is indicated by a broken line 4 ', and the position of the outer surface 4 of the product after processing is indicated by a solid line. The surface 4 has typical surface contours and roughness.

  By the milling of the outer surface, the reaction of the intermediate can be carried out to improve the surface finish and / or to improve the dimensional tolerances of the product 1.

After the reaction of the intermediate, an object is to heat-treat to form a final product at a temperature T3. At least one magnetocalorically active _{La (Fe 1-a-b} Co a Si b) 13 - to form the base phase, at T3> T2, a T3 <T1.

  It was observed that the final product 1 was cracked as it moved from the blast furnace after the last heat treatment. Crack formation is observed in large products, for example in samples having an area of 5 mm or more. It was observed that the formation of cracks in the structure 1 could be avoided if the cooling rate near the Curie temperature was low.

  Similarly, when a product containing a magnetocalorically active phase is heated, the formation of cracks in a product having an area of 5 mm or more can be avoided by reducing the ramp rate of the temperature in the vicinity spreading on both sides of the product's Curie temperature. Observed.

  As a further example, after sintering, the intermediate was cooled from 1050 ° C. to 60 ° C., slightly higher to the Curie temperature of the magnetocalorically active phase, which was 44 ° C. The intermediate 1 was gradually cooled from 60 ° C to 30 ° C.

  Without being bound by theory, the formation of cracks during cooling of the intermediate 1 to room temperature after sintering is related to the negative thermal expansion of the magnetocalorically active phase due to the product passing a Curie temperature of 44 ° C. To do. By reducing the cooling temperature at which the magnetocalorically active phase passes the Curie temperature, cracks can be avoided by reducing the pressure on the product 1.

  FIG. 11 shows that in Example 2 where the intermediate is singulated from two or more separate ones, one or more through-holes extend from one side of the product or channel to the opposite side of the product. It is formed on the surface.

  Line erosion cutting can be used to unify said intermediate 10 to form slices 15, 16 in the example, as well as forming channel 17 in intermediate 10.

  Like the channels 17 formed on the surface, the slices 15 and 16 of the side surface 19 are produced by line erosion cutting. These surfaces have a plurality of ridges in a direction parallel to the material by line cutting.

  The channel 17 may have an area in which the product 18 is arranged for inducing a flow of a heat exchange medium during operation of a magnetic heat exchange apparatus including a magnetocalorically active phase. The magnetocalorically active phase can result in a small amount of a magnetocalorically active phase that acts as a protective coating and / or a corrosion resistant coating.

  Combinations in different processing methods can be used from the above products to the final product. For example, the product is located on the outer surface to provide an outer surface with manufacturing errors. Channels were formed on the surface to provide cooling channels, and the product was singulated into a plurality of final products.

  Without being bound by theory, by working in the state of an intermediate containing permanent magnetism and very little magnetocalorically active phase, the phase change that occurs at the temperature in the region of the magnetic phase transition temperature is related to the avoidance of the phase change. It can't happen in the processing and tension. By avoiding tension in processing in phase change, thermal decomposition and splitting of the substance can be avoided.

It has been clarified that a magnetocalorically active phase such as La (Fe _1-a-b Si _a Co _b ) exhibits a negative volume change at a temperature near the Curie temperature. Products containing these phases can be successfully processed by the methods described herein.

Production of a structure comprising at least a magnetocalorically active La (Si, Co, Fe) ₁₃ base phase for use in a magnetic heat exchange device

As an example, a product containing the magnetocalorically active phase of the La (Si, Co, Fe) ₁₃ system on a 11.5 mm x 5.8 mm area plate contains the expected magnetocalorically active phase and at least 50% alpha-Fe. Is formed by providing an intermediate comprising an amount to form a content of

  These intermediates are processed by line erosion cutting to form multiple plates of the expected size. These plates are further heat treated to form a magnetocalorically active phase.

  The intermediate block was formed by a powder metallurgy technique or a two-step heat treatment.

As a further example, a powder mixture of 7.7 wt% Co, 3.2 wt% Si, 18.7 wt% La is provided by milling the initial powder. This configuration provides a magnetocalorically active phase with a _Tc near + 29 ° C.

In the following powder mixture, a powder mixture of 9.7 wt% Co, 3.2 wt% Si, 18.7 wt% La is provided by milling the first powder. This configuration provides a magnetocalorically active phase with a T _c near + 59 ° C.

  A third powder mixture is produced by stirring the first and next powder mixtures in a 1: 1 ratio to provide a powder comprising a magnetocalorically active phase having a Tc of 44 ° C.

The third powder mixture is compressed at a pressure of 4 ton / cm ² to provide a substrate having an area of 26.5 mm × 21.8 mm × 14.5 mm.

  Later, the substrate was subjected to a two-step heat treatment to form an intermediate block. In particular, the substrate was heat treated under vacuum at 1080 ° C. for 7 hours, cooled to 800 ° C. under argon for 1 hour, held at 800 ° C. for 6 hours, and cooled to room temperature in 1 hour.

  The dwell stage at high temperature facilitates the liquid phase reaction to produce a high density product and form a magnetocalorically active phase. The next dwell stage at low temperature decomposes the magnetocalorically active phase and promotes the formation of an alpha-Fe phase similar to the La, Si-rich phase.

Table 6 summarizes the alpha-Fe content of products formed from powder blends of MPS-1044, MPS-1045, MPS-1046. Each product has a density of 7.25 g / cm ³ and alpha-Fe content of 60.3%, 57.8% and 50.6%, respectively.

  The block was cut as a plurality of plates at 11.5 mm × 5.6 mm × 0.6 mm.

  The sample was heat treated at 1000 ° C., 1025 ° C., and 1050 ° C. for 4 hours under argon to form a magnetocalorically active phase. The entropy change and the Curie temperature were measured by examining the magnetocaloric characteristics and the content of alpha-Fe. These results are summarized in FIG. The content of the alpha-Fe was 50% or more in all the intermediate samples after the heat treatment, but decreased to 7.2% or less.

  The plate was heat treated at 1030 ± 3 ° C. for 4 hours under argon. The results are summarized in FIG.

Block 1 formed from the powder mixture has a _Tc of 28.7 ° C. The change in entropy is 6 J / (kg.K), 43.4 kJ / (m ³ .K), and the content of alpha-Fe is 5.0%.

Block 2 formed from the powder mixture has a _Tc of 43.0 ° C. The change in entropy is 5.2 J / (kg.K), 37.9 kJ / (m ³ .K), and the content of alpha-Fe is 5.0%.

Block 3 formed from the powder mixture has a _Tc of 57.9 ° C. The change in entropy is 4.4 J / (kg.K), 32.2 kJ / (m ³ .K), and the alpha-Fe content is 7.4%.

La (Fe, Si, Co) ₁₃ system configuration shown in reversible phase transition

Without being bound by theory, the reversible phase transitions observed in the La (Fe, Si, Co) ₁₃ system can be understood based on those described in the phase diagram. FIG. 12 shows the case where the ratio of La: (FE + Co + Si) is 1:13, 8% by volume of Co is contained, and the phase change from 600 ° C. to 1300 ° C. is performed when the Si content is 1.5 wt% to 5 wt%. Is a theoretical phase diagram.

The target configuration is shown by drawing a line every 100 ° C. with a Si content of 3.5 wt%. The magnetocalorically active phase is 1/13 (La ₁ : (Fe, Si, Co) ₁₃ , and forms a single phase on the right side of the phase diagram.

It is the target Si content, and from the result of the figure due to the temperature rise, from 600 ° C. to 850 ° C., alpha-Fe, 5/3 (La ₅ Si ₃ ), 1/1/1 (La ₁ (Fe, Co) ₁ The state consisting of Si) ₁ is stable. From 850 ° C. to 975 ° C., the state consisting of gamma (Gamma) -Fe, 1/13 (La ₁ : (Fe, Si, Co) ₁₃ 1/1/1 (La ₁ (Fe, Co) ₁ Si) ₁ is The state consisting of a single phase of 1/13 (La ₁ : (Fe, Si, Co) ₁₃ is stable from 975 ° C. to 1070 ° C. From 1070 ° C. to 1200 ° C., gamma (Gamma) is stable. The state composed of -Fe, 1/13 (La ₁ : (Fe, Si, Co) ₁₃ , and liquid L is stable.

A method for forming a product having a target structure is a liquid phase of gamma (Gamma) -Fe, 1/13 (La ₁ : (Fe, Si, Co) ₁₃ , liquid L at 1100 ° C. In order to decompose the magnetocaloric phase 1/13 (La ₁ : (Fe, Si, Co) _13. In addition, in order to obtain alpha-Fe, 5/3 (La ₅ Si ₃ ), 1/1/1 (La ₁ (Fe, Co) ₁ Si) ₁ , the temperature is lowered to 800 ° C. or lower. After the heat treatment, the product is securely processed, so that the product re-forms the magnetocalorically active phase containing a high 1/13 (La ₁ : (Fe, Si, Co) ₁₃ phase. , Single 1/13 (La ₁ : (Fe, Si, Co) ₁₃ phase The state can be heat-treated at 1050 ° C.

In order to allow movement of these three regions in the phase diagram, the Si content should be in a predetermined region indicated by dashed lines 101 and 102. In particular, the minimum amount of the Si content, a single _{1/13 (La 1: (Fe,} Si, Co) 13 and Gamma _{(Gamma) -Fe, 1/13} (La 1: (Fe, Si, Co ₁₃ , 1/1/1 (La ₁ (Fe, Co) ₁ Si) ₁ and gamma (Gamma) -Fe, 1/13 (La ₁ : (Fe, Si, Co) ₁₃ , liquid phase + L The maximum amount of Si contained is alpha-Fe, 5/3 (La ₅ Si ₃ ), 1/1/1 (La ₁ (Fe, Co) ₁ Si) ₁ and alpha- Fe, 1/13 (La ₁ : (Fe, Si, Co) ₁₃ , 1/1/1 (La ₁ (Fe, Co) ₁ Si) ₁ is determined by the boundary between the regions.

Claims (19)

A method for producing a product in which impurities containing at least one magnetocalorically active phase is 5% by volume or less ,
Providing a intermediate, the intermediate, forming at least one _{(La 1-a M a)} (Fe 1-b-c T b Y c) phase represented by _{13-d X e} Contains elements to get,
0 ≦ a ≦ 0.9, 0 ≦ b ≦ 0.2, 0.05 ≦ c ≦ 0.2, −1 ≦ d ≦ + 1, 0 ≦ e ≦ 3,
M is any one or more of Ce, Pr and Nd,
T is any one or more of Co, Ni, Mn and Cr,
Y is any one or more of Si, Al, As, Ga, Ge, Sn, and Sb,
X is any one or more of H, B, C, N, Li and Be,
The intermediate includes at least one permanent magnetic phase ;
Applying a process for removing a portion of the intermediate;
After giving the process of removing portions of the intermediate, at least one of _{(La 1-a M a)} (Fe 1-b-c T b Y c) magnetocalorically active phase represented by _{13-d X e} Heat treating to produce a final product comprising:
The process of removing a part of the intermediate includes machining, mechanical crushing, polishing, chemical mechanical polishing, electric discharge cutting, linear erosion cutting, laser cutting, drill or water beam cutting. A step of removing a portion of
Method. The method according to claim 1, wherein the intermediate contains 50% by volume or more and 78.3% by volume or less of alpha-Fe. The method according to claim 1 or 2, wherein the intermediate is produced by heat-treating a precursor containing a phase having at least one NaZn ₁₃ type crystal structure. 4. A method according to claim 3, wherein the precursor is heat treated under conditions selected to produce at least one alpha-Fe type phase. The method according to claim 3 or 4, wherein
The intermediate mixing amount of powder containing elements for forming at least one _{(La 1-a M a)} (Fe 1-b-c T b Y c) phase represented by _{13-d X e} To obtain
A method characterized in that the powder is sintered at a temperature T1 in order to produce at least one phase having a NaZn ₁₃ type crystal structure. A method according to any one of claims 3-5,
After the heat treatment at temperature T1, the precursor is further heat treated at temperature T2 to form an intermediate containing at least one permanent magnetic phase, T2 <T1. 7. The method according to claim 6, wherein the T2 is a temperature causing the decomposition of a phase having a NaZn ₁₃ type crystal structure. The method according to claim 6 or 7, wherein
To produce the final product comprising at least one of the magnetocalorically active _{(La 1-a M a)} (Fe 1-b-c T b Y c) of _{13-d X e} phase, said precursor Temperature A method wherein the heat treatment is performed at T3 and T3> T2.   9. The method of claim 8, wherein T3 <T1. A intermediate for synthesizing at least magnetocalorically active phase is unrealized impurities is not more than 5% by volume product,
The intermediate comprises at least one _{(La 1-a M a)} (Fe 1-b-c T b Y c) of _{13-d X e} phase,
0 ≦ a ≦ 0.9, 0 ≦ b ≦ 0.2, 0.05 ≦ c ≦ 0.2, −1 ≦ d ≦ + 1, 0 ≦ e ≦ 3,
M is any one or more of Ce, Pr and Nd,
T is any one or more of Co, Ni, Mn and Cr,
Y is any one or more of Si, Al, As, Ga, Ge, Sn, and Sb,
X is one or more of H, B, C, N, Li and Be;
The intermediate comprises at least one permanent magnetic phase;
Intermediates. An intermediate body according to claim _{10, (La 1-a M} a) (Fe 1-b-c T b Y c) 13-d X composition of the phase of _e is at least one alpha -Fe based An intermediate characterized in that it exhibits a reversible decomposition reaction into a La-rich phase and a Si-rich phase . An intermediate body according to claim 10 or 11, at least one _{(La 1-a M a)} (Fe 1-b-c T b Y c) 13-d of _{X e} composition of the phase is a liquid phase intermediate, and forming at least one _{(La 1-a M a)} (Fe 1-b-c T b Y c) 13-d X e phase by sintering. 13. The intermediate according to claim 11 or 12 , wherein the intermediate includes at least one alpha-Fe type phase, and the alpha-Fe type phase further includes Co and Si. body. An intermediate member according to any one of claims _11~13, B r> _0.35T, and intermediates, which is a _H cJ> 80 Oe. A product comprising at least one magnetocalorically active LaFe ₁₃ based phase, having a magnetic phase transition temperature T _c and having an impurity content of 5% by volume or less ,
Wherein the composition of at least one of LaFe ₁₃ based phase, a selected product to show reversible phase decomposition reaction into at least one alpha -Fe based phase, La-rich phase and Si- rich phase ,
The LaFe ₁₃ base phase is a phase of _{(La 1-a M a)} (Fe 1-b-c T b Y c) 13-d X e,
0 ≦ a ≦ 0.9, 0 ≦ b ≦ 0.2, 0.05 ≦ c ≦ 0.2, −1 ≦ d ≦ + 1, 0 ≦ e ≦ 3,
M is any one or more of Ce, Pr and Nd,
T is any one or more of Co, Ni, Mn and Cr,
Y is any one or more of Si, Al, As, Ga, Ge, Sn, and Sb,
X is one or more of H, B, C, N, Li and Be,
Product . A product according to claim 15, by sintering of at least one of _{(La 1-a M a)} (Fe 1-b-c T b Y c) 13-d composition of Xe phase liquid phase ( La _1-a M _a ) (Fe _1-b-c T _b Y _c ) _13-d Xe product selected to form a phase. A product according to claim 15 or 16, the content of Si is at least one of _{(La 1-a M a)} (Fe 1-b-c T b Y c) 13-d Xe phases at least a Product selected to exhibit a reversible phase decomposition reaction into two alpha-Fe based phases, La-rich phase and Si-rich phase. 10. A product (1; 10; 20) produced by the method according to any one of claims 1 to 9 , comprising at least one magnetocalorically active phase and having a magnetic phase transition temperature _Tc . Use of a product (1; 10; 20) produced by the method according to any one of claims 1 to 9 for magnetic heat exchange.

Images